For cardiac surgeries or the like, an extracorporeal circulation circuit equipped with a blood pump or an artificial lung serving as a substitute for the function of a patient's heart or lung is used. Such an extracorporeal circulation circuit is provided with a blood reservoir (sometimes referred to as a “venous blood reservoir”) for temporarily storing venous blood removed from a patient's vein and adjusting the blood volume in a circulating circuit, and a blood reservoir (sometimes referred to as an “cardiotomy reservoir”) for aspirating, collecting, and temporarily storing blood (intracardiac blood) flowing out of the operative field. As compared to the venous blood, the intracardiac blood contains a high proportion of air bubbles or extraneous materials, such as pieces of flesh, fats, and clots, so the cardiotomy reservoir is provided with a cardiotomy section composed of a filter for removing extraneous materials and a defoamer for defoaming. Storing both of the venous blood and the intracardiac blood in a common blood reservoir is also widely practiced.
FIG. 13 is a cross-sectional view illustrating an example of a general configuration of a conventional cardiotomy section 900. The cardiotomy section 900 includes a filter 910 having a generally cylindrical shape as a whole and a defoamer 920 having a generally cylindrical shape and located inside the filter 910. Generally disk-shaped resin plates 931 and 932 are bonded to the upper and lower edges of the filter 910. The defoamer 920 is held by being bonded to the upper resin plate 931. The upper resin plate 931 has a through hole 933 formed in the center thereof. A conduit tube 935 that introduces intracardiac blood into the cardiotomy section 900 is inserted in the through hole 933 (see Patent Document 1, for example).
A mixing vessel 940 is connected to the upstream side of the conduit tube 935. A space in the mixing vessel 940 is divided by a partition wall 943 into a blood flow channel 941 for the flow of blood and a liquid medicine flow channel 942 for the flow of a liquid medicine. The conduit tube 935 is connected to an opening 944 formed in the underside of the mixing vessel 940. The partition wall 943 roughly divides the opening 944 into two sections.
Blood (intracardiac blood) 951 aspirated from an operative field flows through an intracardiac blood inflow port 950, the blood flow channel 941 and the opening 944 in the mixing vessel 940, and the conduit tube 935 in sequence, and then into the cardiotomy section 900.
In the case of adding a liquid medicine to the blood in the cardiotomy section 900, a liquid medicine 961 is injected into a liquid medicine injection port 960 and flows through the liquid medicine flow channel 942 and the opening 944 in the mixing vessel 940 and the conduit tube 935 in sequence, and then into the cardiotomy section 900.    Patent Document 1: JP2002-165878A